586,681 research outputs found
Asymptotic power-law tails of massive scalar fields in Reissner-Nordstr\"{o}m background
We investigate dominant late-time tail behaviors of massive scalar fields in
nearly extreme Reissner-Nordstr\"{o}m background. It is shown that the
oscillatory tail of the scalar fields has the decay rate of at
asymptotically late times. The physical mechanism by which the asymptotic
tail yields and the relation between the field mass and the time
scale when the tail begins to dominate, are discussed in terms of resonance
backscattering due to spacetime curvature.Comment: 18 pages, 1 figure, accepted for publication in Physical Review
Long-tail Relation Extraction via Knowledge Graph Embeddings and Graph Convolution Networks
We propose a distance supervised relation extraction approach for
long-tailed, imbalanced data which is prevalent in real-world settings. Here,
the challenge is to learn accurate "few-shot" models for classes existing at
the tail of the class distribution, for which little data is available.
Inspired by the rich semantic correlations between classes at the long tail and
those at the head, we take advantage of the knowledge from data-rich classes at
the head of the distribution to boost the performance of the data-poor classes
at the tail. First, we propose to leverage implicit relational knowledge among
class labels from knowledge graph embeddings and learn explicit relational
knowledge using graph convolution networks. Second, we integrate that
relational knowledge into relation extraction model by coarse-to-fine
knowledge-aware attention mechanism. We demonstrate our results for a
large-scale benchmark dataset which show that our approach significantly
outperforms other baselines, especially for long-tail relations.Comment: To be published in NAACL 201
Time-lapse CCD imagery of plasma-tail motions in Comet Austin
The appearance of the bright comet Austin 1989c1 in April-May of 1990 allowed us to test a new imaging instrument at the Joint Observatory for Cometary Research (JOCR). It is a 300mm lens/charge coupled device (CCD) system with interference filters appropriate for cometary emissions. The 13 frames were made into a time-lapse movie showing the evolution of the plasma tail. We were able to follow at least two large-scale waves out through the main tail structure. During the sequence, we saw two new tail rays form and undergo similar wave motion
Multiscale nature of the dissipation range in gyrokinetic simulations of Alfv\'enic turbulence
Nonlinear energy transfer and dissipation in Alfv\'en wave turbulence are
analyzed in the first gyrokinetic simulation spanning all scales from the tail
of the MHD range to the electron gyroradius scale. For typical solar wind
parameters at 1 AU, about 30% of the nonlinear energy transfer close to the
electron gyroradius scale is mediated by modes in the tail of the MHD cascade.
Collisional dissipation occurs across the entire kinetic range
. Both mechanisms thus act on multiple coupled scales,
which have to be retained for a comprehensive picture of the dissipation range
in Alfv\'enic turbulence.Comment: Made several improvements to figures and text suggested by referee
Statistics of Weak Gravitational Lensing in Cold Dark Matter Models; Magnification Bias on Quasar Luminosity Functions
We compute statistical properties of weak gravitational lensing by
large-scale structure in three Cold Dark Matter models. We use a PM
-body code to simulate the formation and evolution of large-scale structure
in the universe. We perform ray-tracing experiments for each
model using the multiple lens-plane algorithm. From the results of these
experiments, we calculate the probability distribution functions (PDF) of the
convergences, shears, and magnifications, and their root-mean-square (rms)
values. We find that the rms values of the convergence and shear agree with the
predictions of a nonlinear analytical model. We also find that the PDFs of the
magnifications have a peak at values slightly smaller than , and
are strongly skewed toward large magnifications. In particular, for the
high-density model, a power-law tail appears in the magnification distribution
at large magnifications for sources at redshifts . The rms values of the
magnifications essentially agree with the nonlinear analytical predictions for
sources at low redshift, but exceed these predictions for high redshift
sources, once the power-law tail appears.
We study the effect of magnification bias on the luminosity functions of
high-redshift quasars, using the calculated PDFs of the magnifications. We show
that the magnification bias is moderate in the absence of the power-law tail in
the magnification distribution, but depends strongly on the value of the
density parameter. In presence of the power-law tail, the bias becomes
considerable, especially at the bright end of the luminosity functions.Comment: 24 pages, 9 figures, LaTex using epsfig.sty. Submitted to the The
Astrophysical Journa
Aerodynamic characteristics of a 1/6-scale model of the rotor systems research aircraft with the rotors removed
A wind-tunnel investigation was conducted to refine the aerodynamic characteristics of the rotor systems research aircraft. For the investigation, a 1/6-scale model without a main rotor or a tail rotor was used. The model provided the capability for testing different engine nacelle sizes, engine pylon fairings, and tail configurations. The engine thrust effects were modeled by small engine simulators (fans). Data were obtained primarily over an angle-of-attack range from -13 deg to 13 deg at several values of sideslip. Stability characteristics and control effectiveness were investigated. The model with the scaled engine nacelles and the combination T-tail and lower horizontal tail displayed longitudinal and lateral-directional stability. Results show that by reducing the horizontal or vertical-tail span the longitudinal stability is decreased. Reducing the engine nacelle size increases the static stability of the model. Effective dihedral is essentially zero at 0 deg angle of attack and 0 deg wing incidence
Using Cluster Abundances and Peculiar Velocities to Test the Gaussianity of the Cosmological Density Field
(Abridged) By comparing the frequency of typical events with that of unusual
events, one can test whether the cosmological density distribution function is
consistent with the normally made assumption of Gaussianity. To this end, we
compare the consistency of the tail-inferred (from clusters) and measured
values (from large-scale flows) of the rms level of mass fluctuations for two
distribution functions: a Gaussian, and a texture (positively-skewed) PDF.
Averaging the recent large-scale flow measurements, we find that observations
of the rms and the tail at the 10 h^-1 Mpc scale disfavor a texture PDF at ~1.5
sigma in all cases. However, taking only the most recent measurement of the
rms, that from Willick et al. (1997b), the comparison disfavors textures for
low Omega_0=0.3, and disfavors Gaussian models if Omega_0=1 (again at ~1.5
sigma). Predictions for evolution of high temperature clusters can also be made
for the models considered, and strongly disfavor Omega_0=1 in Gaussian models
and marginally disfavor Omega_0=1 in texture models. Only Omega_0=0.3 Gaussian
models are consistent with all the data considered.Comment: 34 pg incl. 8 embedded figures, LaTeX, aaspp4.sty, submitted to Ap
Low-speed wind-tunnel investigation of a large scale advanced arrow-wing supersonic transport configuration with engines mounted above wing for upper-surface blowing
Tests have been conducted in a full scale tunnel to determine the low speed aerodynamic characteristics of a large scale advanced arrow wing supersonic transport configuration with engines mounted above the wing for upper surface blowing. Tests were made over an angle of attack range of -10 deg to 32 deg, sideslip angles of + or - 5 deg, and a Reynolds number range of 3,530,000 to 7,330,000. Configuration variables included trailing edge flap deflection, engine jet nozzle angle, engine thrust coefficient, engine out operation, and asymmetrical trailing edge boundary layer control for providing roll trim. Downwash measurements at the tail were obtained for different thrust coefficients, tail heights, and at two fuselage stations
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